#!/usr/bin/env python
#encoding latin1

class pila:
	def __init__(self):
		self.count = 0
		self.vector = list()
	def apilar(self,dato):
		self.vector.append(dato)
		self.count += 1
	def ver_tope(self):
		if not self.count > 0:
			return None
		return self.vector[self.count - 1]
	def desapilar(self):
		if not self.count > 0:
			return None
		self.count -= 1
		return self.vector.pop()
